Embodiments described herein relate to the field of intraocular implants for use in ophthalmic treatments. More particularly, embodiments described herein are related to the field of intraocular pressure (IOP) control systems, for use in ophthalmic treatments.
Glaucoma, a group of eye diseases affecting the retina and optic nerve, is one of the leading causes of blindness worldwide. Most forms of glaucoma result when the intraocular pressure (IOP) increases above normal for prolonged periods of time. IOP can increase due to high resistance to the drainage of the aqueous humor relative to its production rate. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision.
The eye's ciliary body continuously produces aqueous humor, the clear fluid that fills the anterior segment of the eye (the space between the cornea and lens). The aqueous humor flows out of the anterior chamber (the space between the cornea and iris) through the trabecular meshwork and the uveoscleral pathways, both of which contribute to the aqueous humor drainage system. The delicate balance between the production and drainage of aqueous humor determines the eye's IOP.
FIG. 1 is a diagram of the front portion of an eye that helps to explain the processes of glaucoma. In FIG. 1, representations of the lens 110, cornea 120, iris 130, ciliary body 140, trabecular meshwork 150, and Schlemm's canal 160 are pictured. Also shown in FIG. 1 are posterior chamber 170 and anterior chamber 175. Anatomically, the anterior segment of the eye includes the structures that cause elevated IOP which may lead to glaucoma. Aqueous humor fluid is produced by the ciliary body 140 that lies beneath the iris 130 and adjacent to the lens 110 in the anterior segment of the eye. This aqueous humor washes over the lens 110 and iris 130 and flows to the drainage system located in the angle of the anterior chamber. The angle of the anterior chamber, which extends circumferentially around the eye, contains structures that allow the aqueous humor to drain. The trabecular meshwork 150 is commonly implicated in glaucoma. The trabecular meshwork 150 extends circumferentially around the anterior chamber. The trabecular meshwork 150 seems to act as a filter, limiting the outflow of aqueous humor and providing a back pressure that directly relates to IOP. Schlemm's canal 160 is located beyond the trabecular meshwork 150. Schlemm's canal 160 is fluidically coupled to collector channels (not shown) allowing aqueous humor to flow out of the anterior chamber. The arrows in the anterior segment of FIG. 1 show the flow of aqueous humor from the ciliary bodies 140, over the lens 110, over the iris 130, through the trabecular meshwork 150, and into Schlemm's canal 160 and its collector channels.
One method of treating glaucoma includes implanting a drainage device in a patient's eye. The drainage device allows fluid to flow from anterior chamber 175 to a drainage site outside the eye, relieving pressure in the eye and thus lowering IOP. These devices are generally passive devices and do not provide a smart, interactive control of the amount of flow through the drainage tube. In addition, fluid filled blebs frequently develop at the drainage site. The development of the bleb typically includes fibrosis, which leads to increased flow resistance; it is generally the case that this resistance increases over time. The development and progression of fibrosis reduces or eliminates flow from anterior chamber 175, reducing the capacity of the drainage device to affect IOP. While many implanted drainage devices incorporate micro-electro-mechanic systems (MEMS), state-of-the-art devices have separate tubing sets and components to operate as fluidic routes. The tubing sets are crudely glued onto the active MEMS device using adapters and complex clamping structures to connect the fluidic parts.
Therefore, there is a need for simple and compact MEMS packages to provide fluidic paths in implanted devices for IOP control.